Partitioning beta diversity in a subtropical broad‐leaved forest of China

Abstract

Abstract. The classical environmental control model assumes that species distribution is determined by the spatial variation of underlying habitat conditions. This niche-based model has recently been challenged by the neutral theory of biodiversity which assumes that ecological drift is a key process regulating species coexistence. Understanding the mechanisms that maintain biodiversity in communities critically depends on our ability to decompose the variation of diversity into the contributions of different processes affecting it. Here we investigated the effects of pure habitat, pure spatial, and spatially structured habitat processes on the distributions of species richness and species composition in a recently established 24-ha stem-mapping plot in the subtropical evergreen broad-leaved forest of Gutianshan National Nature Reserve in East China. We used the new spatial analysis method of principal coordinates of neighbor matrices (PCNM) to disentangle the contributions of these processes. The results showed that (1) habitat and space jointly explained ;53% of the variation in richness and ;65% of the variation in species composition, depending on the scale (sampling unit size); (2) tree diversity (richness and composition) in the Gutianshan forest was dominantly controlled by spatially structured habitat (24%) and habitat-independent spatial component (29%); the spatially independent habitat contributed a negligible effect (6%); (3) distributions of richness and species composition were strongly affected by altitude and terrain convexity, while the effects of slope and aspect were weak; (4) the spatial distribution of diversity in the forest was dominated by broad-scaled spatial variation; (5) environmental control on the one hand and unexplained spatial variation on the other (unmeasured environmental variables and neutral processes) corresponded to spatial structures with different scales in the Gutianshan forest plot; and (6) five habitat types were recognized; a few species were statistically significant indicators of three of these habitats, whereas two habitats had no significant indicator species. The results suggest that the diversity of the forest is equally governed by environmental control (30%) and neutral processes (29%). In the finescale analysis (10 3 10 m cells), neutral processes dominated (43%) over environmental control (20%).

More than environmental control at local scales: do spatial processes play an important role in floristic variation in subtropical forests?

“…In smaller spatial scales, a spatially structured environment may favor limitations in the dispersion of species, and neighboring environments tend to be similar (Karst et al 2005). This fact is very clear in the studied hillside, because the strongest predictive variables (elevation and slope) were spatially structured along the gradient, as also observed by Legendre et al (2009).…”

“…A fraction related to spatially structured environment (R 2 = 8%) may also be used to justify the distance-decay floristic similarity (DinizFilho et al 2012). Legendre et al (2009) andDiniz-Filho et al (2012) suggest that a spatially structured environment has an influence on the spatial distribution of species, because as distance between environments increases, the higher their difference in terms of species composition. In smaller spatial scales, a spatially structured environment may favor limitations in the dispersion of species, and neighboring environments tend to be similar (Karst et al 2005).…”

“…Despite the relevance of environmental factors as indicators of species distribution along gradients (e.g., Gentry 1988;Toledo et al 2012), a more recent ecological approach takes into account both the spatial structure of plant communities and environmental factors, especially the influence of spatial structure on variations in species composition (Lichstein et al 2002;Legendre et al 2009;Eisenlohr et al 2013;Gasper et al 2013;Mélo et al 2013;Oliveira-Filho et al 2013;Lewis et al 2014). Spatial structure may be caused by contagious ecological processes such as dispersion (Legendre 1993;Cottenie 2005), but environmental factors may also have spatially structured fractions in space, because neighbor sites tend to present similar environmental characteristics (Fortin & Dale 2005).…”

Stochastic distribution of small soil eukaryotes resulting from high dispersal and drift in a local environment

“…Emerging evidence suggests that both groups of processes jointly regulate ecological communities (Chave, 2004) with varying relative effects depending on geographic scales and strength of environmental gradients (see Hanson et al, 2012) and type of organism (body size, dispersal mode, see Soininen et al, 2007). At smaller scales, habitat heterogeneity declines, which generally results in lower habitat preference and therefore greater importance of stochastic processes over deterministic factors (Legendre et al, 2009;Chase, 2014). However, the evolutionary and ecological factors that influence dispersal of organisms may also diminish with decreasing geographic scale (Warren et al, 2014).…”

Taxonomic groups with lower movement capacity may present higher beta diversity

“…Accordingly, several studies have demonstrated a host of different factors that may influence variation of species composition through space: (1) spatial and environmental gradients (e.g. Clark et al, 1999;Nekola & White, 1999;Oliveira-Filho & Fontes, 2000;Carneiro & Valeriano, 2003;Steinitz et al, 2006Steinitz et al, , 2007bLegendre et al, 2009); (2) differences in the physiology, in the degree of biological interactions and in the dispersal ability of the species (Nekola & White, 1999;Tuomisto et al, 2003;Gilbert & Lechowicz, 2004); (3) barriers imposed by the configuration of the landscape and the influence of weather on species' dispersion (Nekola & White, 1999;Hubbel, 2001); (4) stochastic processes generated randomly and independently of environmental dissimilarities (Neutral Theory sensu Hubbel, 2001;Soininen et al, 2007b;Steinbauer et al, 2012); (5) species' tolerance to fragmentation (Arroyo-Rodríguez et al, 2013); (6) spatial scale (extension, resolution; Nekola & White, 1999;Steinitz et al, 2006;Soininen et al, 2007b;Arroyo-Rodríguez et al, 2013). Therefore, more accurate analysis involving other variables could yield further explanations regarding the spatial distribution observed in this study.…”